1. Field of the Invention
The present invention relates to data processing and aircraft navigation. More particularly, this invention relates to methods and systems for airlines and others to better track and predict future aircraft trajectories so as to yield increased aviation safety and airline operating efficiency.
2. Description of the Related Art
Many complex methods for the tracking and prediction of material flows and the future position of particular assets as a function of time have been developed. However, as applied to the aviation industry, such methods often have been fragmentary and/or have not addressed the present and future movement of the aircraft and other aviation assets in relation to actions that can alter the aircraft's future trajectory.
Aviation regulatory authorities (e.g., various Civil Aviation Authorities (CAA) throughout the world, including the Federal Aviation Administration (FAA) within the U.S., are responsible for matters such as the separation of in-flight aircraft through an Air Traffic Control (ATC) system. In this task, the CAAs collect and disseminate considerable data concerning the location of aircraft within the airspace system. This data includes: radar data, verbal position reports, data link position reports (ADS), etc. Airlines and other aircraft operators have developed their own flight following systems as required by the world's CAAs, which provide additional information concerning the position and future path of the aircraft. Additionally, third parties have developed their own proprietary systems to track aircraft (e.g., Passur).
In the current art, the use of these data sources is done by various, independent agencies, airlines or third parties. There appears to have been few successful attempts by the various airlines/CAAs/airports/third parties to develop accurate prediction process that encompass all of the real time events (weather, ATC, individual pilot decisions, secondary factors, maintenance requirements, turbulence, etc.) that can effect the trajectory of an aircraft. For example, in the tracking and prediction of an aircraft trajectory into an airport, it often happens that some critical elements are left out of the prediction that can have a significant impact on the accuracy of the predicted arrival/departure times.
An example of one of these elements is the ATC system's response to too many aircraft trying to land at an airport in a defined period of time. In the current art, the prediction of the aircraft trajectory encompassing the arrival/departure time is predicated on the current aircraft position, speed, flight path and possibly winds. Yet as the aircraft nears an overloaded airport, the ATC controller will often begin to slow down the aircraft to move it back in time.
This process is analogous to the “take a ticket and wait” approach used in other industries. To assure equitable service to all customers, as the consumer approaches a crowded counter, the vendor sets up a ticket dispenser with numbered tickets. On the wall behind the counter is a device displaying “Now Serving” and the number. This “first come, first serve” process assures that no one customer waits significantly longer than any other customer.
The effect of the ATC's “take a ticket and wait” solution on arrival/departure aircraft is to add 1, 5, 10, 15 or more minutes to the arrival/departure time. It is a goal of the present invention to encompass the effect of this “too many aircraft” and other factors in the development of more accurate, flight trajectory prediction methods.
Another aspect of the current art is the industry's use of single trajectory prediction methods. Those now doing aircraft trajectory predictions typically only look in detail at the current leg of an aircraft's flight schedule.
To better track and predict an aircraft trajectory encompassing the arrival/departure of an aircraft/aviation asset, it is first necessary to understand the aviation processes surrounding the flight of an aircraft. FIG. 1 has been provided to indicate the various segments in a typical aircraft flight process. It begins with the airline/pilot filing of an Instrument Flight Rules (IFR) flight plan with the applicable CAA. Next the pilot arrives at the airport, starts the engine, taxis, takes off, flies the flight plan (e.g., route of flight), lands and taxis to parking. At each stage during the movement of the aircraft on an IFR flight plan, the CAA's ATC system must approve any change to the trajectory of the aircraft. Further, anytime an aircraft on an IFR flight plan is moving, an ATC controller is responsible for maintaining adequate separation from other IFR aircraft.
During the last part of a flight, typical initial arrival sequencing (accomplished on a first come, first serve basis, e.g., the aircraft closest to the arrival airport is first, next closest is second and so on) is accomplished by the enroute ATC center near the arrival airport (within approximately 100 miles of the airport), refined by the arrival ATC facility (within approximately 25 miles of the arrival airport), and then approved for arrival by the ATC tower (within approximately 5 miles of the arrival/departure airport).
For example, current CAA practices for managing arrivals at many airports involve sequencing aircraft arrivals by linearizing an airport's traffic according to very structured, three-dimensional, aircraft arrival/departure paths, at a considerable distance from the airport. For a large hub airport (e.g., Chicago, Dallas, Atlanta), these paths involve specific geographic points that are separated by approximately ninety degrees; see FIG. 2. Further, if the traffic into an airport is relatively continuous over a period of time, the linearization of the aircraft flow is effectively completed hundreds of miles from landing. This can significantly restrict all the aircraft's arrival/departure speeds and alter the expected arrival/departure time, since all the aircraft in line are limited to that of the slowest aircraft in the line ahead, regardless of the aircraft's current speed.
Much of the current thinking concerning the airline/ATC delay problem is that it stems from the over scheduling by the airlines of too many aircraft into too few runways, see FIG. 3. While this may be true in part, it is also the case that the many apparently independent decisions that are made by an airline's staff (see FIG. 4 for an outline of the typical airline internal production processes) and various ATC controllers may significantly contribute to airline/ATC delay problems. And while many of these decisions are predictable, in the current art they have yet to be accounted for in the real time prediction of the trajectory of that aircraft.
The temporal variations in the arrival/departure times of aircraft into an airport can be quite significant. FIG. 5 shows for the Dallas-Ft. Worth Airport the times of arrival/departure at the airport's runways for the aircraft arriving during the thirty minute time period from 22:01 to 22:30. It can be seen that the numbers of aircraft arriving during the consecutive, five-minute intervals during this period were 12, 13, 6, 8, 6 and 5, respectively. Effectively, the ATC system deals with each aircraft as it arrives in the local area for landing. This leads to inconsistent aircraft flows, which, in turn, leads to inefficient use of the runways, which leads to delays that affect the predicted arrival time.
These delays are especially problematic since they are seen to be cumulative. FIG. 6 shows the percentage of aircraft arriving on time during consecutive one-hour periods throughout a typical day for all airlines and a number of U.S. airports. This on time arrival/departure performance is seen to deteriorate throughout the day. This supports the need for a long trajectory prediction as a twenty-minute delay can carry forward to all future flight segments planned for that aircraft throughout the day or, even worse, carry forward to other aircraft or even into the next day as, for example, crews switch aircraft or become illegal.
Another example of last minute changes to the flight's expected arrival/departure time stems from current aviation authority rules requiring different spacing between aircraft based on the size of the aircraft. Typical spacing between the arrivals of aircraft of the same size is three to four miles, or approximately one minute based on normal landing speeds. But if a small (Learjet, Cessna 172) or medium size aircraft (B737, MD80) is behind a heavy aircraft (B747, B767), this spacing distance is stretched out to five to six miles or one and a half to two minutes for safety considerations.
Thus, it can be seen that if a sequence of ten aircraft is such that a heavy aircraft alternates every other one with a small aircraft, the total distance of the arrival/departure sequence of aircraft to the runway (6+3+6+3+6+3+6+3+6+3) is 45 miles. But if this sequence develops to put all of the small aircraft in positions 1 through 5, and all of the heavy aircraft in slots 6 through 10, the total distance of the arrival/departure sequence of aircraft to the runway is only 35 miles (3+3+3+3+3+4+4+4+4+4) since the spacing between the aircraft is three or four miles. Since within the current art of arrival flow management the arrival sequence is allowed to develop randomly, the arrival/departure time can vary considerably from this one factor alone.
Unfortunately, to correct over capacity problems in the current art, the controller only has one option. They take the first over-capacity aircraft that arrives at the airport and move it backward in time. The second such aircraft is moved further back in time, the third, even further back, etc. Without a process in the current art to move aircraft forward in time or alter the arrival/departure sequence in real time, the controller has only one option—delays.
Further, the problem is compounded by the fact that traffic congestion is dealt with manually and piece-wise. Controllers and pilots solve traffic flow problems locally within small and somewhat disconnected airspace sectors without knowing the ripple effects propagating to other airspace sectors.
Clearly it is better to solve the problem in a coherent, coordinated and consistent manner, but this is not done in the current art. Yet to accomplish a coherent, coordinated and consistent solution, it is first necessary to have a comprehensive view of the airspace (including its capacity and ideally the capacity of all the interconnected assets such as gates, runways, customs, etc) that includes the trajectories and predictions of all arriving and departing flights as defined within the present invention. Further, it is clear that this is a complex problem that cannot be solved manually.
The current art of aircraft arrival/departure sequencing to an airport or other system resource that can effect the arrival prediction, can be broken down into seven distinct tools used by air traffic controllers, as applied in a first come, first serve basis, include:
Structured Dogleg Arrival/Departure Routes—The structured routings into an arrival/departure are typically designed with doglegs. The design of the dogleg is two straight segments joined by an angle of less than 180 degrees. The purpose of the dogleg is to allow controllers to cut the corner as necessary to maintain the correct spacing between arrival/departure aircraft.
Vectoring and Speed Control—If the actual spacing is more or less than the desired spacing, the controller can alter the speed of the aircraft to correct the spacing. Additionally, if the spacing is significantly smaller than desired, the controller can vector (turn) the aircraft off the route momentarily to increase the spacing. Given the last minute nature of these actions (within 100 mile of the airport), the outcome of such actions is limited.
The Approach Trombone—If too many aircraft arrive at a particular airport in a given period of time, the distance between the runway and base leg can be increased; see FIG. 7. This effectively lengthens the final approach and downwind legs allowing the controller to “store” or warehouse in-flight aircraft.
Miles in Trail—If the approach trombone can't handle the over demand for the runway asset, the ATC system begins spreading out the arrival/departure aircraft flows linearly. It does this by implementing “miles-in-trail” restrictions. Effectively, as the aircraft approach the airport for arrival/departure, instead of 5 to 10 miles between aircraft on the linear arrival/departure path, the controllers begin spacing the aircraft at twenty or more miles in trail, one behind the other; see FIG. 8.
Ground Holds—If the CAA separation authorities anticipate that the approach trombone and the miles-in-trail methods will not hold the aircraft overload, aircraft are held at their departure point and metered into the airspace system using assigned takeoff times.
Holding—If events happen too quickly, the controllers are forced to use airborne holding. Although this can be done anywhere in the system, this is usual done at one of the arrival/departures to an airport. Aircraft enter the “holding stack” from the enroute airspace at the top; see FIG. 9. Each holding pattern is approximately 10 to 20 miles long and 3 to 5 miles wide. As aircraft exit the bottom of the stack towards the airport, aircraft orbiting above are moved down 1,000 feet to the next level.
Reroute—If a section of airspace, enroute center, or airport is projected to become overloaded, the aviation authority occasionally reroutes individual aircraft over a longer lateral route to delay the aircraft's entry to the predicted congestion.
CAA's current air traffic handling procedures are seen to result in significant inefficiencies and delays, not fully accounted for in the arrival/departure predictions of the current art. For example, vectoring and speed control are usually accompanied with descents to a common altitude, which may change the aircraft's groundspeed, and therefore the actual arrival time. These actions taken by the controller are usually done in the last 20 to 30 minutes of flight, and while applications of the current art can recognize this effect in real time after the fact, they do not predict that these events will occur as is done in the present invention.
Thus, despite the above noted prior art, airlines/CAAs/airports/third parties continue to need more accurate methods and systems to better track and predict the trajectories of a plurality of aircraft into and out of a system resource, like an airport, or a set of system resources.
3. Objects and Advantages
There has been summarized above, rather broadly, the prior art that is related to the present invention in order that the context of the present invention may be better understood and appreciated. In this regard, it is instructive to also consider the objects and advantages of the present invention.
It is an object of the present invention to provide a method and system to better track and predict aircraft trajectories for a given number of hours into the future, with respect to a plurality of aircraft into and out of a specified system resource, like an airport, or set of resources, thereby overcoming the limitations of the prior art.
It is further object of the present invention that, although some steps of the present invention must be accomplished in order (i.e., one must collect the specified data before a trajectory can be built), other actions can be accomplished in any order (i.e. the long trajectory can be built prior to the ATC/weather/secondary factors are applied), while still other actions are accomplished in the order necessary.
It is another object of the present invention to present a method and system for the real time tracking and prediction of aircraft that takes into consideration a wider array of real time parameters and factors that heretofore were not considered. For example, such parameters and factors may include: aircraft related factors (e.g., speed, fuel, altitude, route, turbulence, winds, weather), ground services (gates, maintenance requirements, crew availability, etc.) and common asset availability (e.g., runways, airspace, Air Traffic Control (ATC) services).
It is another object of the present invention to provide a method and system that will enable the airspace users to better manage their aircraft by continuously and more accurately predicting the location of each aircraft along a forward looking time line x hours into the future—a long trajectory.
It is a further object of the present invention to provide a method and system that analyzes large amounts of real time information and other factors simultaneously, identifies system constraints and problems as early as possible, tracks the position of each aircraft, predicts multi segment arrival/departure times for each aircraft, and continuously monitors these predictions for changes.
It is still a further object of the present invention to temporally track and predict the arrival/departure times of aircraft into or out of a specific system resource in real time. Further, if ongoing events alter demand or capacity such that demand is above system capacity, it is then the object of the present invention to account for these problems in the arrival/departure predictions within the present invention.
Such objects are different from the current art, which typically tracks and predicts aircraft arrival times for a single flight, does not account for all of the outside factors that can alter the aircraft's trajectory, nor builds “long trajectories” necessary to more accurately predict multi segment arrival/departure times into the future.
These and other objects and advantages of the present invention will become readily apparent, as the invention is better understood by reference to the accompanying drawings and the detailed description that follows.